With the 25th anniversary of the Tiananmen Square crackdown less than a month away, China has launched a broad effort to muzzle and detain citizens who are attempting to remember the victims.

On Tuesday, authorities detained human rights lawyer lawyer Pu Zhiqiang and at least five other activists who’d attended a Tiananmen seminar in Beijing three days earlier.

Then, on Thursday, state media reported that authorities had “criminally detained” prominent journalist Gao Ju _ once jailed for her writings during the 1989 protests _ and accused her of sharing a government document with a foreign website.

The detentions, coupled with other recent actions against activists associated with the Tiananmen protests, are a further demonstration that Chinese President Xi Jinping plans to take a hard line on free speech, even as he preaches the need to “open up” and reform China’s economy.

Cao thinks the stepped-up police action is related to the significance of the 25-year anniversary, as well as internal worries about maintaining control. “This year, the Chinese Communist Party feels particularly vulnerable,” said Cao, noting that there have been recent protests in Taiwan and Hong Kong against Beijing’s influence.

For nearly a quarter century, China’s communist party has effectively banned any public mention of the Tiananmen protests, which drew thousands to Beijing’s central square for weeks, and the military’s response, in which hundreds of people died. When people type “June 4” into Baidu, China’s main search engine, they get a message in Chinese that says: “According to policies from relevant laws and regulations, part of the search result cannot be displayed.”

William Nee, a Hong Kong-based China researcher for Amnesty International, said the government’s recent actions were “an attempt at forced amnesia.” He noted that President Xi delivered a speech in January in which he said Chinese leaders needed to balance social stability with the demand for justice. “But their default when they get into trouble is to fall into a ‘stability above all’ mindset,” he said.

The arrest of Pu Zhiqiang stunned many in Beijing. Pu is a well-known lawyer, having represented artist Ai Weiwei and other dissidents. At one time he seemed in the good graces of the government, quoted prominently in state media as part of a successful campaign to end forced-labor camps.

Last Saturday, Pu gathered at a private home with a dozen other Beijing intellectuals. The group urged a probe of the 1989 military assault on the pro-democracy protesters. As they did five years ago, those in attendance posed for a photo that was posted on social media.

Three days later, authorities detained Pu for “picking quarrels and causing trouble.” At least four others at the meeting also were detained, according to media reports and human rights groups.

Hu Jia, a pro-democracy activist who’s effectively been under house arrest in Beijing for a decade, told McClatchy he was surprised that authorities “cracked down so fast and so severely.” There were no detentions of Pu and others when the group met openly five years ago. “The punishment is drastically different this time,” Hu said in a telephone interview.

On Wednesday, U.S. State Department spokesman Jen Psaki urged China to release Pu and others and “guarantee them the protections and freedoms to which they are entitled under China’s international human rights commitments.” A major Chinese newspaper, the Global Times, responded Friday, publishing a commentary that accused Pu of belonging to a group of activist lawyers “who have wild intentions to challenge and change the law.”

The criminal detention of Gao has also dismayed human rights activists, partly because China invoked its broad “state secrets” law to detain the 70-year-old journalist. Gao is accused of leaking a government document to a foreign website. State media reported that she’d confessed to the crime, a confession that Amnesty International and other groups thought was coerced.

State media didn’t name the document Gao allegedly leaked, but there’s wide speculation that it was “Document No. 9,” which gained international attention when the Hong Kong-based Mingjing Monthly published it last August. The document laid out the government’s plans for maintaining ideological controls in China. On Friday, however, the magazine’s publisher denied that Gao was the source of “Document No. 9,” adding to uncertainties about what she’s accused of leaking.

Gao was first arrested on June 3, 1989, when a Hong Kong newspaper published a story she wrote in support of the pro-democracy protests in Tiananmen Square. She was in detention 14 months. In the 1990s, she served six years in prison, accused of leaking government documents she’d obtained.

The recent detentions follow a string of others across China. Ding Zilin, 77, the founder of a group of relatives known as the Tiananmen Mothers, has reportedly been forced out of Beijing until after the June 4 anniversary. In March, security agents detained He Yang, a Beijing-based documentary maker, when he tried to visit Ding at her home.

In the southern city of Guangzhou, authorities have detained at least six people who attended a trial and expressed solidarity with Li Weiguo, an activist convicted of “inciting illegal assembly.” Li’s alleged crime was to seek official permission to hold a candlelit vigil in Guangzhou to remember the Tiananmen Square victims.

Cao, who was born in northern China, notes that there have always been “sensitive days” in which authorities have little tolerance for public gatherings or dissent. These include meetings of the National People’s Congress and visits to China by foreign dignitaries.

Now, she said, “The number of sensitive days has grown and the number of people who have been subjected to surveillance and restriction of movement has grown.”

Hu said that, in his case, he was under constant surveillance and unable to leave his home to meet friends or anyone else. He said he’d gotten in early trouble with authorities when he took a wreath to Tiananmen Square on June 4, 2004. Active in environmental causes and advocacy for AIDS victims, Hu spent three years in jail after publicly criticizing the selection of China to host the 2008 Olympics. He was released in 2011.

Now 40, Hu said he’d spend June 4 with candles lit. He plans to wear nothing but black to reflect his “sadness and anger” for the suppressed memories of what happened 25 years ago.

McClatchy special correspondent Tiantian Zhang contributed to this report.